Circle-gauging instrument



M w, 1923.- mamas H. J.-ADAMS CIRCLE GrAUGrIIWrv INSTRUMENT o i in- 11 Filed June 7, 1920 2 Sheets-Sheet 1 Jufiy w, 1923. mmfi H. J. ADAMS v CIRCLE GAUGQING INSTRUMENT Original Filed June 7, 1920 2 sheets-sheet Patente July 10, 12923.

HERBERT J. ADAMS, or :eArT L onnnK, MICHIGAN.

CIBGLE-GAUGlNG INSTRUMENT.

Application filed June '7, 1920, Serial T 0 all whom. it may concern Be it known that I. Hnnsnm J. ADAMs, a citizen of the United States, residing-at Battle Creek, in the county of Calhoun and State ofMichigan, have invented a new and useful Improvement in Circle-Gauging Instruments, of which the following is a specification.

The purpose of my invention is to provide a compact andefiiciently operative instrument in which are combined means by Which:

All circles and arcs thereof that mechanical andlcivil engineering draftsmen may need to gauge, measure or draw, of range in size between a straight line and'a circle of a half inch or less in diameter;

For measuring, or by its aid determining the lengths ofarcs and their radii, and their value in degrees;

For setting off the degrees of the central angles of circles and ruling angles equivalentthereto of segments of circles;

For reproducing curved lines already drawn at the same or diiferent scales;

Providing in a single instrument the means for accomplishing drafting that now requires the use of a large number of pieces of drafting equipment such as fixed curve rules, circle ruling devices of limited range of applicability, and protractors.

I attain these objects by the mechanism and associated objects illustrated in the accompanjyingdrawings, in which Figure 1 is a plan view of my invention as it appears flat on the drafting board, and shows in dash line changed positions of the principal moving members. Fin: 2 is a sec tional vie v ofthe instrument through line X-X, Fig. 1. Figs. 3 and 4 are respectively plan view andv sectionof .the transverse plate 'and channel along which it slides, latch plate and arrangement, of the center pin. Fig, 5 is an ele ation ofthe laterally tapering sleeve which controls the heightof the center pin. Figs. 6 and Tare respectively plan and sectional details showing; the bearing ball frame supporting feet 42, and the support for guide bars 5. Figs. 8 and, 9 are respectively end and sectional views oi? theslowmoving screw rib-bed turning knob. Figs. 1.0, 11 and 12 are vertical. and sectional details of the connection of the stay bar 13 withihcflex-ible bar 6. Figs. 1 3. and 14 areperspective views showing the No. 387,241. Renewed Iliay 28, 1923.

means on radial arms 7 for their sliding engagement with bars 5. Numbered parts herein are so numbered in the views.

v The angle bar 1, slashed; and bent into suitable shape, with the lipsofthe slashes securely riveted-orbolted together, the plate 2 fastened thereto by bolts 3, and having one edge concaved in right andleft intersecting divisions which serve as guides 4, hereinafter referred to, the pair of curved guidebars 5 supported by the bars 45 and the ends of the angle bar, and also hereinafter referred to, and a channel 17 fastened to bar 1 and plate 2 in line directedmidway between the right andleft guides, constitute the framework of my V Q a its operating position being flatwise on and about the drafting board; I find it convenient to form the angle bar to describe three angles of .120. degrees each, and the edge ofplate 2 opposite the guides thereon may describe a straight linedirectedtowards corresponding points on the outline of the frame, so that angles of 30, 60,.90 and 120 degrees can be conveniently set ofi .by the frame alone. i i v Except .where obviously unsuitable, or otherwise indicated, all the parts ofthe instrument are preferably stamped from sheet. metal. t

- Pprovide the normally straight flexible bar 6. which has fastened to its ends "the arms 7 which are provided at one end with the perforated guide lugs 8 (Fig. 14) adjacent to the bar, the latterbeing fastened to the arms by the inverted channels, or bights 12, which grip it. Said lugs 8, and lugs 9 formed at the opposite ends of the arms are'provided for sliding engagement of, the arms with the bars 5 and guides 4 respectively, lugs 8, in preferredxconstruction (Fig. 14), overlapping bars 5, and being flared for required. play for the swing ofthe arms 'in their travel along guides 4,

while the downwardly projecting hooks provided on pull rods 27', hereinafter men tioned, serve to holdthe arms inclose sliding engagement with bars 5flthroughout their length. The lugs 9 terminate in pointers L0 (Figsfl. and 13.) hereinafter referred 'to. The inner edges 11 ofsaid arms are in line perpendicular, or normal, to the ends of the curvable portion of bar 6. That bar is preferably made of spring steel the greatest, uniformity of texture 'known to commerce, and it stands edgewise to the drafting board and the planes of said arms.- -Movement of the arms forces bar 6 into uniform curves. 7

The stay bar 13 1s provlded, having guides thereon for sliding engagement with the c1rcular guide ltwhich is fastened to the frame clear of the swinging movement of arms 7 and centers at the midway point of swing the arms to force the bar into curve formations; The ends of'bar 6, by means connected therewith hereinafter described, are'simultaneously started and swung in unison along said guides to the extreme curved position of the bar, wherein lugs 9 maatxthfe intersecting-point of guides 4, or are stopped atxany intermediate po- 'sition (dash line Fig. 1), said arms 7being each swung 90 degrees 1n total movement;

and at such meeting position said inner ,edges are .in line with each other and said intersecting point, and on the line of the chord of said extreme, or half circle, forr mation, said bights 12 having been in line of the tangents, and said inner edges .in

line of the radii in all of the curve formations of bar Gin such 90 degree swing, said guides 41: and 5 being geometrically de signed and located to dispose the arms in positions with respect to said bar which enforce therein uniformity of curve formations throughout, guides 4: enforcing are relation of curve to tangent, while guides 5 enforce arc relation of curve, chord and tangent, So that in any'of said curve formations any portion of thecurved bar will other portion thereof.

register exactly on a line drawn along any v A simple test of thefefi'ects of certain kinds of control on a bar similar to bar 6 may be found in employlng'a flexible'b'ar of uniform texture and dimensions, say a flexible machinists rule; By simply pushing its ends towards each other without gripping them it will be noticed that theend portions will re straight or only slightly curved, while towards the center of the bar it becomesbowed to a short curve formation.v

On the nther hand, by gripping the ends, and whlle pulllng them away from each other forclng the ends into curves, the cen- A, tral portionofthebar will form a companatively fiat,.jbut irregular, curve,

I Such. formations are produced by casual or" a jbir trary control as. distinguished from the geometrical control gauged by the properties of circles necessary'for producing in the bar uniform curves. The bar 6 will overcome considerable friction and return to a straight line formation upon being re leased from bowed position. Guides 4 are in form and position in my invention describing a line which would be intersected by equal length sectors of radii of a suc cession of arcs of gradually shortened cir cles of length equal to one half the length of the bar imaginable between a straight line and a curve of the greatest degree possible to eitherh'alf, which is one fourth circle in my c'onstructionQ The guides- 5 have the effect of describing. a linejwhich would be intersected by the ends of the above mentioned successlon of arcs extending as in the above case from the midway point of the bar which is always stationary. But for convenience in the use of the instrument guidesb are set away from the ends of the flexible portion. of the bar 6 at thepoint of the flattest curve formations a "short distance on the tangent thereof, as

shown inFigure l, and swingsgradually nearer to lines at right angles tofthe successive chords, and according as the tangential angles increase in degree. Hence the necessity for the flare in lug '8-men tioned which allows for the necessarily in creasing obliqueness of the positions of the a tangent lines across bars 5; I

A scale, 16,0f degrees, shown in part in Fig.1, is arranged along one of the guideskt, preferably the left hand one as shown and for reasons hereinafter indirated, for indicating by the corresponding pointer 10 on arm'7 the number of degrees bar 6 has been curved from position at rest,

the number per degree of curve equalling the number describing half the length of the bar. the outside end of'thescale being.

zero,while the spaces thereon become graduallynarrower towards the inner end in llO' agreement with the shortening of the curve formations enforced by the arms 7 in their progress'along guides 4. The number of degrees to be pointed off on the scaleffor each degree of curve depends. upon the length of said bar, such number of degrees being increased or decreased by multiplication or division to; indicate respectively the number of degreesat which the bar'should ment, preferably in my construction that obtaining in the United States for curve formulae. i. e100 feet'to the inch. i

A scale 40 (shown in part, Fig. 10) is arranged along. bar 6 for measuringthe length. of any are or portion thereof'formed by it, and'for verifying and proving the besetto accommodate: it to the desired curve of a smaller or larger scale'ofmeasurement than that adopted for the instrurecites curves gauged thereby, such scale being also convenient in connection'with radius arms 7 for use as a protractor by pointing off on bar 6 the required number of degrees to the unit on the scale for the degree of curve to which the baris set up, said radius arms being used, upon registering the bar on the curved line, for drawing sectors of the legs of the desired angle,

The bar 6 may be of any length for convenient use on a drafting table; yet the convenience of the scale 470 depends upon the length of the bar. If the bar is 9 or 18 inches long, for a degree to a space of the scale, when it is setup to half a circle, they should he graduated respectively to 20ths and 10ths inches, such arrangement being convenient for civil engineers, the longer being especially adapted for railroad work. If it is desired for mechanical drafting to have'the scale spaced to 16ths of an inch, a bar 115,- inches long would have spaces equal to 180 degrees atthe half circle formation, and be convenient for both the above classes of work. liars ,of other lengths could have a scale for lineal measurement on one side of the'bar and a scale for degrees on the other. According to the formula mentioned a bar of any length when set to a 1 degree curve would describe an are having a central angle of as many degrees as there were inches in its length. A bar 15 inches long with a scale thereon spaced to 12ths of an inch, equalling 180 spaces when at the "half circle, would be especially convenient as a protractor, since from the one degree curve formation it would be possible to set off an angle of th of a degree, or 5 minutes.

The end walls of channel 17 continue upward forming lugs 18 which have corresponding slots extending below the top of the channel. A screw, 28, carrying'turning knob 29, extends lengthwise through the channel and is provided with annular grooves near 'its ends affording the screw revolving seating in said slots and confining it longitudinally in the channel, while means hereinafter mentioned confine it vertically therein. Plate 22 rests on and extends to the right and left of said channel correspondingly, being adapted for sliding movement along the same, and carries rigid beneath it auxiliary channel, or sleeve, 23 (Fig. 4) which slides in channel 17 and encloses the screw, and serves to hold the plate on and guide it along the channel, the end portions of said plate being turned down and provided with openings 24 in which the hook-shaped lever arms 25 slide, said lever arms being pivoted to the'wings 26 of the channel, while their opposite ends have pivoted to them pull rods 27 provided with hooks, or offsets, hereinbefore mentioned, which pass through the holes in lugs 8; so

that movement of plate 22 along the channel swings the'lever arms and changes the formation of bar 6. it portion of the lever arms which have contact with the .plate is curved, subjecting the lever arms to centrifugal reaction as the openings progress along them, which advances their ultimate, or functional, ends over longer arcs than the arcs of the same radii between whose'subtending radii the fulcrum moves.

Plate 22 is surmounted over the channel by lug 30 (Fig. 4), pivoted to which is latch plate 31 which in turn carries pull lug 46, and has at one end a forked tongue projecting downward at the edge of plate 22 into the channel adapted for engaging the threads of the screw, said latch plate being adapted to tip into and out of such engagement, and being provided with release lug 32 between which and plate 22 tension spring 33 is anchored for automatically latching the latter plate on the chan nel subject to releasing pressure on either lug 32, or 46 in connection with opposite pressure respectively against the forward or rearward end "of the channel. Plates, or caps, 20 and 21 which serve as pull lugs in moving plate 22, as above, are fitted to said lugs 18 and extend into the annular grooves on the screw for completing close bearin s therefor in the channel, the pressure required being conveniently applied by thumb and finger of the operator, said caps correctly extending sufficiently high above the channel to afford such purchase. Screw 28 serves as a slow-moving screw affect-ing directly, the latch plate by turning knob 29 for setting the pointer 10 up to the exact point desired on the degree scale 16, or stopping the arms 7 at desired positions by reference to members thereon hereinafter mentioned. i

The turning knob has ribs parallel with the screw and equally spaced apart so that the knob can be turned rib by rib by a finger or thumb alone, and its revolutions tal lied by divisions thereof enabling the operator, by reference to the known number of revolutions required for a space on said degree scale, or scale 44 hereinafter described-a matter usually of easy mental calculation-to move said pointer or other members to desired positions between graduation marks on the adjacent measuring scales.

Plate 34 (Fig. 4) is provided which has a bight 20, serving as pull lug and screw bearing as hereinbefore mentioned, and passes around the point dividing guides 4 and is fastened to plate 2 beneath it by the same means fastening as is employed for the channel 17. Extending through sleeve, 19, swcdged in holes in vertical line in plate '34 is center pin- 35 which is, with said sleeve let into said dividing point a distance equal to 2; its diameter. The. pin is adaptedto revolve in the sleeve, and has a needle point at its lower end and a head at the top. En-

. closing the pin between its head and plate shortest curve possible in my invention with the flexible bar 6 of convenient length for generaluse, I complement such capacity by the use of nearly allof the parts involved therein by providing bar 37 (Fig. 1); supported along and. a little above one of the arms 7, preferably the right hand one suming bar 6 to be at the forward side of the instrument) by fastening a lug provided thereon at its center to a corresponding upwardly pro ecting lug on the arm 7 The bar extends nearly to bight 12 and to lug 9,

' leaving said arm edge 11 clear forruling along it. Said bar 37 has offsets at each end projecting over the drafting board in which areprovided clear of said arm the openings 38 adapted for seating marking implements I therein by providing barfiTFig. 1 (supvent flow of ink from such instrument thereto. Adjacent to said. openings. are provided the upwardly projecting and flaring walls forming sockets 39 for steadyingsuch implements upright. Said barr37 is vertically flexible from the center outward, permitting depression of1said seats to such greater'or less extent as is necessary for the implement tovreach the drafting paper according .to the widthof linethe implement isfifixed to produce, affording equally firm and definite seating in'case of differing widths of line. The seats are used in connection with said center pinwhen sticking the drafting board and forming an axis around which the frame may be revolved, for guiding such implecircles or segments thereof I avoid in large measure the soillng drag that would be otherwise occasioned by the instrument thus far described in its contact therewlth "in moving it about, and avoid in. large measure the friction otherwise to be I encountered in. revolving it about the pin,

by providing units of the following device at appropriate points (Figs. 1. 6 and 7);

diaphragm, ll having a round hole in its floor and being provided with a shank wh ch is fastened to the under side of the frame,

I preferably underneath plate 2, in. which is no a corresponding hole. Enclosed in the diaphragmis bearing ball 42, in diameter greater than the depth .of the diaphragm. Ten- S1011, plate 4-3 is fastened on top of the frame I by bolt3, and at rest bears against theupper hole' and, subject to overcoming downward pressure on they frame, holds the ball to 1 vprotrusion through the lower hole, but not far enoughto deprive'it of revolving play therein, thoughv extending below the lower plane of the instrument, adapting the ball to hold adjacent portions of the instrument clear of the drafting board. Upon theframe being depressed to the board by overcoming the tension plate'the ball is forced to protrude through the upper hole. Though the,

frame may be revolved directly by hand, with the ball supports it is easily revolved, especially in case of the larger circlestraced or. ruled by the pen seats, by lateral pressure of the seated marking instrument against the seats;

scale, 44, guides 4 and adjacent to the pen seats by which may be indicated respectively, in connection with pointer and the. outer pen seat, the distances of the inner and outer pen seats from the center pin at any distance the arms 7 may be stopped along said guides, thus indicating the radiusof the arcs or circles gauged or formed by the use of the pen seats, the scale having no reference to the actual distance travelled by the pointer along guide l, but only to the actual radial distances of the pen seatsgfrom the center in. I

In each of the several models which I have (Fig. 6) is arranged along and have experimented with in perfecting m invention lestimate that the bar 6 employed in each has been sprung to a half circle formation several hundreds of, times without discovering harmful deformation 7 thereof, due largely no, doubtto maintaining the uniformity claimed for the curve formations.

Having thus described my invention, what I claim as new, and desire'to secure by Letters Patent, is

1. In a circle gauging instrument, including a frame work adapted for being moved 0 about or revolved on jadrafting board, which ments about the pm 111 mfiand 2:- framework embraces a bar having evenly I projecting parallel end portions, abracing plate therefor, and a channel in linedirected midway saidendportions, and including a revolvable vertical pin on said plate midway its forward edge adapted for lowering and sticking the board for revolving the frame thereon, a plate transverse to the vchannel having openings in its ends with means for its sllding engagement along the tened to theright and left of the frame .cor-

overlapping said guide edges, adapting the arms when the bar is sprung to throw it into uniform curves for gauging and ruling circles in series of limited range; pen seat members mounted on said arms adapted for seating marking implements of, differing sizes and guiding them around the pin as the frame is revolved for gauging and ruling circles in series of limited range including a range complementing those possible with the bar; a screw adapted to revolve in said channel in longitudinally confined position; a transverse plate having openings in its ends and being provided with a sleeve member enclosing the screw for affording the plate sliding guided engagement with andalong the channel; right and left lever arms pivoted to the channel and slidably confined in said openings and connected by rods wit-h said arms and adapted for being actuated by movment of the plate to change the form of the flexible bar and the distance between the. pen seats and the pin; a spring- -held latch pivotally mounted on the plate provided with release and pull lugs and a slotted tongue adapted for engagement with the threads of the screw for stopping the plate the flexible bar and guides being provided with scale indicia adapted for measuring the value of the curves of the bar in degrees, their'lengths and central angles and the distances of the pen seats from the pm, so thatthe combined range of application of said bar and pen seats in connection with saidscales in gauging and ruling circles extends from a straight line to a circle a half inch or less in diameter; a turning knob member on said screw provided with equally spaced ribs parallel therewith for turning the screw by divisions thereof rib by rib and tallying the revolutions to slowmove said arms by reference to the known number of such revolutions required for a space on the guide scales to given distances that fall between graduation marks on said scales; substantially as described.

5. Ina circle gauging instrument, a frame adapted for being moved about on a drafting board embracing right and left guide bars, a plate having intersecting curved guides and a channel fastened to the plate in line directed midway of the guides; a pin pivotally mounted on the frame at the intersection point of said guides adapted for and provided with means for holding it clear thereof; a normally straight flexible bar having arms fastened to its ends projecting per endicularly therefrom, and provided with means for their sliding engagement with the guides, and having mounted thereon pen seat members for guiding marking implements about the pin, the arms being adapted for carrying the pen seats towards or away from the pin and to throw the bar into uniform curves as it is sprung, the pen seats and bar being adapted respectively for gauging and ruling circles in smaller and larger mutually complementing series; a transverse plate having openings at its right and left ends and means for its slidable engagement with and along said channel and for stopping and releasing it; a pair of lever arms pivoted to the channel and connected with the arms by rods and slidably confined in said openings and adapted for beingv actuated by opening adapted subject to pressure on the frame to hold the ball in the lower opening with revolving play therein for holding the adjacent portion of the instrument off the drafting board when it is being moved about in use of the bar or revolved in use of the pen seats, and to permit upon such pressure the ball to protrude through the upperopeningand allow the frame to come to rest on said board, but otherwise to hold it to serve as a supporting roller for said frame; substantially as described and shown. 6. In a circle gauging instrument the combination of a framework embracing right and left guides and a channel in line directed midway between the guides; a normally straight flexible bar'anda pair of arms other and so guided throwing the bar into uniform curves upon its being sprung, for V gauging and ruling circles in series of limited range; a transverse plate and means affording it sliding engagement along said channel and for stopping it thereon and re leasing it; a pair of lever arms pivoted to the channel and connected with the arms by,

a pair of rods, said'lever arms being slid- I ably confined in right and left'openings in said transverse plate adapting them for being actuated by movement of the plate for moving the arms and curving the bar; a clip adapted to impinge on the flexible bar midway its length; a stay bar having one end vertically pivoted tothe clip; a curved guide fastened to the frame clear of the swing of the arms and centering at said midway point; guide lugs on the stay bar affording it sliding engagement with said curved guide, said stay bar being adapted upon downward pressure thereon for steadying the flexible bar on the drafting board and for being swung to clear either side of the flexible bar either in straight or curved form: substantially as described and shown.

7. in a drafting instrument, the combination of a frame, a flexible bar, a. center bar provided with a center pin, an adjusting screw mounted on said center bar, an adjusting slide mounted on said center bar and detachably engageable with said screw per Jnitting its adjustment by said screw or in dependently thereof, actuating levers pivotally mounted on said center bar and operatively associated with said slide whereby said levers are actuated by the adj ustmcnt of the slide, links connecting the ends of said actuatinglevers to the ends of said flexible bar uide arms secured to the ends of sail.

flcxibde bar and disposed at right angles thereto when said bar is in its normal. position, curved guide members on said fr ue coacting with the ends of said arms, curved guide bars operatively associated With the ends of said flexible bar, a brace for said flexible bar engaging the center thereof, and a segment on which the outer end of said brace bar is adjustably mounted.

8. In a drafting instrument, the combination of a frame, a flexible bar, arenter b- 1' provided with a center pin, adjusting}; screw mounted on said center bar, an ad j usting slide, mounted said center bar and detachably engageable with said screw pen niitting its adjustment by said screw ndependently thereof, actuating levers pivotally mountedon saidcenter bar and 0138 1- tively associated with said slide whereby said levers are actuated by the adjustment of the slide, inks connecting the ends of said actuating levers to the ends of said flexible bar, guide arms secured to the ends of said flexible bar and disposed at right angles thereto when said bar is in its: normal position, curved guide members on said frame reacting with the ends of said arms, and curved guide bars operatively associated with the ends of said flexible ear. I

9. In a drafting instrument, the combination of a frame, a flexible bar, a center bar provided with a center pin, an adjusting slide mounted on said center bar, actuating levers pivotally mounted on said center bar and operatively associated with said slide whereby said levers are actuated by the adjustment of the slide, links connecting the ends of said actuating levers to the ends of said flexible bar, guide arms secured to the ends of said flexible bar and disposed at right angles thereto whensaid bar is in its normal position, curved guide members. on said frame coacting with the ends of said arms, curved guide bars operatively associated with the ends of said flexible bar, a brace for said flexible bar engaging the center thereof, and a segment on which the outer end of said brace bar is adjustably mounted.

l0. Ina drafting instrument, the combination of a frame, a flexible bar, a center bar provided with a center pin, an adjusting slide mounted on said center bar, actuating levers pivotally mounted on said center bar and operatively associated with said slide whereby said levers are actuated by the adjustment of the slide, links connecting the ends of said actuating levers to the ends of said flexible bar, guide arms secured to the ends of said flexible bar and disposed at right angles thereto when said bar is in its normal position, curved guide members on said frame coacting with the ends of said arms, an d curved bars operatively associated with theends of said flexible bar.

11. In a drafting instrument, the combination of a frame, a flexible bar, a center bar provided with a center pin, an adjustingscrew mounted on said center bar and detachably engageable with said screw per-.

mitting its adjustment by said screw or independently thereof, actuating levers pivotally mounted on said center bar and operatively associated with said slide whereby said levers are actuated by the adjustment of the slide, links connecting the ends of said actuating levers to the ends of said flexible bar, means for maintaining a uniformity of curvature of said flexible bar throughoutits adjustment, a brace for said i flexible bar engaging the center thereof, and

a segment on which the outer end ofsaid brace bar is adjustably mounted.

12. in a drafting instrument, the combination of a frame, a flexible bar, a center bar provided with a center pin, an adjusting screw mounted on said center bar, an adjusting slide mounted on said center bar and detachably engageable with said screw permitting its adjustment by said screw or independently thereof, actuating levers pivotally mounted on said center bar and operatively associated with said slide whereby said levers are actuated by the adjustment of the slide, links connecting the ends of said actuating levers to the ends of said flexible bar, and means for maintaining a uniformity of curvature of said flexible bar throughout its adjustment.

13, In a drafting instrument, the combination of a frame, a flexible bar, acenter bar provided with a center pin, an adjusting screw mounted on said center bar and detachably engageable with said screw permitting its adjustment by said screw or independently thereof, irregularly curved actuating levers pivotally mounted on said center bar and operatively associated with said slide whereby said levers are actuated by the adjustment of the slide, links conneeting the ends of said actuating levers to the ends of said flexible bar, andmeans for maintaining a uniformity of curvature of said flexible bar throughout its adjustment.

14;. In a drafting instrument, the combination of a frame, a flexible bar, an adjusting screw disposed transversely of. said bar, an adjusting slide detaehably engageable with said screw permitting its adjustment by said screw or independently thereof, operating connections from said slide to the ends-of said flexible bar, guide arms secured to the ends of said flexible bar, guide members coacting with the ends of said arms, and curved guide bars operatively associated with the ends of said flexible bar, said flexible bar, guide bars, and arm guide members being provided with scale indicia.

nation of a frame, a flexible bar. an adjust ing slide adjustable transversely of said flexible bar, operating connections from said slide to the ends of said flexible bar, guide arms secured to the ends'of said flexible bar, guide members eoacting with the ends of said arms, and curved guide bars operatively associated with the ends of said flexible bar, said flexible bar guide bars, and arm guide members being provided with scale indicia.

17. In a drafting instrument, the eombi nation of a frame, a flexible bar, an adjusting slide adjustable transversely of said flexible bar, operating connections from said slide to the ends of said flexible bar,

guide arms secured to the ends of said flexible bar, guide members coacting'with the ends of said arms, and curved guide bars operatively associated with the ends of said flexible bar. I

18. In a drafting instrument, the combination of a frame, a flexible bar, an adjust mg slide mounted for adjustment trans versely of said flexiblebar, operating con neetions from said slide to the ends of said bar, and means coaeting with the ends of said bar for maintaining uniformity of ourvature thereof throughout its adjustment.

1 9. In a circle gauging instrument provided with an operating framework, the combination of a flexible bar adapted for registering upon drawn lines and for guiding markers alongits surface,a pair of arms fastened to the, ends of the bar adapted for sliding movement on the frame, means on the frame for pulling saidvends and arms towards each other to bow the bar, means on the frame for so controlling the movement of the arms that the bar is forced into uniform curve formation throughout,

.means on the frame and on the bar for measuring by reference respectfully to the positionof the arms and the length of the curve formations or sectors thereof of the bar the geometrical values of such formations, substantially as and for th'e purpose set forth. i

HERBERT J. ADAMS. 

